Integrated amplifiers — Musical Fidelity A1

The A1 is a Class A integrated amplifier from Musical Fidelity that revives the company's model of the same name first sold in 1985. The 2023 generation keeps the specifications, appearance and circuit of the original, and changes only components chosen to lower noise or meet current requirements. It sells for GBP 1,499 in Britain and AUD 3,000 in Australia. The low, slim chassis has a top surface formed entirely as a ribbed heat sink, which carries away the heat of the output stage.

Key specs that matter

Rated output is 25 W per channel into 8 ohm in Class A, backed by 42.5 V peak-to-peak voltage swing and 25 A peak-to-peak current. Gain is 42 dB in Normal mode and 32 dB in Direct mode, damping factor is 150, signal to noise ratio is 82 dB and channel separation is 85 dB. Frequency response runs from 10 Hz to 40 kHz within +0 and -1 dB. Line inputs take 300 mV nominal and up to 8 V, with 25 kohm input impedance. The MM phono input offers 40 dB of gain into 50 kohm and 100 pF for 5 mV cartridges, while the MC input offers 60 dB into 1 kohm for 450 microvolt types. The case measures 440 x 68.3 x 283.3 mm and weighs 10.5 kg, and consumption peaks at 130 W with zero draw in standby.

Engineering and use context

A fully discrete, symmetrical circuit forms the power stage, with two Planar Audio output transistors per channel. It works as a dynamic Class A design - when a load asks for more than the standing current, it slides smoothly into Class AB instead of switching, and can then reach about 40 W into 4 ohm. The new transformer has dual mono split rail windings, so left and right draw on independent supplies of doubled capacity with lower ripple. Preamplifier stages use TL071 JFET devices, and the phono section is a discrete current-mode design. Volume passes through a motorised ALPS RK potentiometer, operated from an infrared remote that controls level only. The Direct switch cuts gain by 10 dB by bypassing a gain block, a setting intended for sensitive speakers and high-output digital sources. Mains is set internally to 230 V or 115 V, with 100 V as an option.

Pairing

Five RCA line inputs and one MM/MC phono input cover a turntable plus several line sources, and a fixed tape output and a variable preamp output with 100 ohm impedance allow a recorder or an external power amplifier or subwoofer. One pair of 4 mm binding posts takes the speaker cables. With its modest Class A rating, efficient speakers of moderate impedance make the most sense.

Alternatives

Musical Fidelity's M6xi integrated amplifier is a far more powerful model that adds HDMI eARC, USB-C and a built-in DAC.